From the introduction:
Combat II is a unified system which successfully integrates physical combat, movement, and spell/psionic use on one time scale. It assumes the use of miniatures as well as the playing group's concerns for better "realism" and battle tactics than what the Players Handbook offers.
Coupled with the Phase Initiative System, at the heart of Combat II is the Magic System (which incorporates two versions of mana points). You will also find some miscellaneous rules concerning several integrated "critical hit/miss rules."
Just another set of house rules? Have a look...
The product is distributed as two ASCII text files - (1) a brief introduction/explanation, and (2) the lengthy alternate rules. The product also circulated in Word for Windows format as well as a formula spreadsheet for Excel.